Agricultural vehicles are used under a wide range of operating conditions. The vehicles are used outdoors and may be required to traverse a paved road to move from a storage facility to a field and then traverse an unpaved surface getting to and working in the field. The vehicles may further be required to operate at varying speeds or under varying loads depending on the type of crops, tillage method, or the particular application being performed.
Sprayers, as a specific type of agricultural vehicle, may apply liquid or dry products, such as fertilizers, herbicides, and/or pesticides to a field. The sprayer typically includes a holding tank in which the product may be loaded prior to transport to a field or while in the field. The sprayer may subsequently travel to the field and apply the product to the field. Certain products may be applied prior to or shortly after planting, prior to emergence of the crop. Other products may need to be applied during the various stages of the growth cycle of the crop. In order to control the track and/or control the rate at which product is applied to the field, the speed at which the vehicle is traveling and the flow rate at which the product is dispensed must be known.
Historically, sprayers have utilized a radar signal to determine the speed at which the sprayer is travelling. The radar signal is transmitted from a radar source mounted to the sprayer, reflected off an external object and returned to a receiver on the sprayer. The radar system generates a pulse train, corresponding to the speed at which the vehicle is traveling and provides the pulse train to an input on a rate controller. The rate controller may then adjust the flow rate of the product being dispensed according to the pulse train input to maintain a desired application rate of the product being dispensed.
Because the sprayers are operated outdoors and throughout the growing cycle, they are subject to a wide variety of operating conditions that may impact the speed feedback signal. Varying weather conditions, such as rain, obstructions in the field, or the crops, such as wheat or corn, as they grow may interfere with the radar signal transmitted from the sprayer. As a result, the speed feedback signal may be inaccurate and the sprayer may apply an undesired amount of product to the field.
Thus, it would be desirable to provide an improved system of determining the speed at which the sprayer is traveling.